The hydrolysis of oxiranes to 1,2-diols is well known to be promoted by strong acid. As indicated in U.S. Pat. No. 3,028,434, prior commercial methods for producing ethylene glycol involved the reaction of ethylene oxide and water in the presence of sulfuric acid.
More recently, industrial processes for the catalytic conversion of ethylene oxide to ethylene glycol typically involve no catalyst. Absence of a catalyst is due to the difficulty incurred during the separation of homogenous acids, such as sulfuric acid or phosphoric acid, from the product mixtures. Presently, standard conditions employ a twenty molar excess of water over the oxide under batch conditions, of one hour residence time, at 150.degree. to 204.degree. C. and 200 psig. Selectivity of the industrial processes undertaken under the aforementioned conditions is reported as follows: ethylene glycol (88%), diethylene glycol (10%), triethylene glycol (2%), with a total glycol product of about 94.5%.
The objective of U.S. Pat. No. 3,028,434, was to provide an effective catalytic process for the manufacture of ethylene glycol by catalytic hydration of ethylene oxide in the presence of a solid catalyst characterized by high selectivity and high thermal stability. The solid catalysts described in the U.S. Pat. No. 3,028,434 were based on zeolite A and zeolite X. These zeolites suffered from the disadvantage of relative instability to steam, which was an inevitable component of the catalytic hydrolysis of ethylene oxide.
Ethylene and propylene glycols are produced in tremendous capacity throughout the world. A principle route to these materials involves the hydrolysis of the corresponding hypoxide. By significantly lowering the required temperature as well as shortening the residence time, in a catalytic conversion based on a steam stable catalyst, through put for a given plant can be increased.